SGT official website explains revised 2021 sporting regulations.
https://supergt.net/news/single/20719
I had misread new sporting regulations.
*Allowing twice updates to the front diveplanes during the season seems to mean left diveplane and right diveplane.
*In a word, GT300/GT300MC can use two types of front diveplanes and
two types of rear wings in the season. That is, LDF and HDF specs.